Motor-fan unit with thermal device

ABSTRACT

A motor-fan unit includes a thermal device serving to monitor the operating temperature of the motor-fan unit. The thermal device is secured to the motor-fan unit through a frictional fit between the thermal device and a cavity provided in an end plate assembly and the field laminations of the motor-fan unit.

The present invention generally relates to motor-fan units. More particularly, the present invention relates to the placement of a thermal device within a motor-fan unit. Most particularly, the present invention relates to a motor-fan unit having a thermal device assembly that is mounted in a cavity in a motor bracket portion, sandwiched between the motor bracket portion and the field laminations of the motor-fan unit.

BACKGROUND OF THE INVENTION

Electronic motors and generators are well known in the art and have been put to use in a variety of applications. One application is the handling of air by what will be termed herein as a “motor-fan unit.” In these motor-fan units, an electric motor is coupled with a fan to create a flow of air to be employed for any of a number of purposes, for example, to draw a vacuum. Often, the fan is used not only to produce a flow of useful air but also to provide cooling air to the motor. A fan mounted on a shaft driven by the motor draws air into a fan shroud to compress or pressurize the air. The pressurized air is released into the motor housing to flow across the motor windings to draw heat into the flow and exhaust it from the motor housing.

Referring to FIG. 1, a motor-fan unit is generally indicated by the numeral 10. Motor-fan unit 10 includes motor assembly 12 and fan assembly 14. Motor-fan unit 10 includes electric motor 16 with an armature or winding 17, commutator 18, and brushes that provide a connection from the power source to commutator 18 and windings 17. Shaft 20 is supported on suitable bearings such that it can freely rotate and is connected to commutator 18 so as to rotate therewith. A field coil 19 generates a magnetic field to cause the rotation.

Motor assembly 12 is configured with commutator 18 closest to fan assembly 14. Fan assembly 14 of motor-fan unit 10 includes fan 26 coupled to one end 27 of shaft 20, as by nut, such that it rotates therewith. Fan assembly 14 is received by diffuser assembly 28 (a radial diffuser is shown, but other diffuser assemblies, such as a ported diffuser could be employed), and shroud 30 encapsulates both diffuser assembly 35 and fan 26. As known in the art, shroud 30 is provided with axial port 31, coaxial with axis A of shaft 20, through which outside air is drawn by fan 26. As shaft 20 and thus fan 26 is rotated by motor 16, fan 26 draws in air at port 31 and forces the air through diffuser assembly 35, which is configured to distribute air as needed according to the desired use of motor-fan unit 10. The motor assembly 12 includes an end plate assembly, generally indicated by the numeral 35, to enclose the motor and support the brushes. The end plate assembly 35 generally includes a planar plate portion 36, which may be annular as shown, and, a motor bracket portion 37 extending from the plate portion toward the motor 16. The bracket portion 37 is adapted to support the motor assembly 15.

These motor-fan units may be sealed or unsealed systems, and may permit differing degrees of air flow through the system. A more open system, with good air through flow, typically runs at high amps, while a more sealed system, with poorer air through flow, runs at lower amps. In operation, each system builds up heat that can destroy motor parts if permitted to build, and, therefore, thermal devices are often employed to monitor the temperature or amperage or both of a motor-fan unit and shut down the motor when the temperature being monitored rises above a set selected threshold.

As shown in FIG. 2, in the prior art, the thermal device 40 is mounted to the field coil 19 with Mylar™ tape 41 and cable ties 42, and is used to monitor the heat and/or amperage at the field coil 19. However, while the field coil 19 does get hot as the motor-fan unit is operated, its heat does not accurately correspond with the heat building up in the motor-fan unit as a whole. For instance, in a sealed system in which the motor-fan unit runs as low amps, the field coil is significantly cooler than in open systems where the motor-fan unit runs at higher amps. Nevertheless, the heat build up in the sealed system is often greater than that built up in the open system because the heat cannot easily escape from the sealed system. Thus, monitoring the temperature and/or amperage at the field coil is not necessarily advisable nor is it necessarily very accurate in conveying information about the actual heat build up in the system. Additionally, the mounting of the thermal device with cable ties and tape adds additional manufacturing complication and cost.

Thus, there exists a need in the art for a new concept for the placement of a thermal device in a motor-fan unit. The thermal device should monitor an area of the motor-fan unit that more accurately reflects the heat building up in the system, and should be mounted in a manner more easily and inexpensively manufactured.

SUMMARY OF THE INVENTION

A motor-fan unit comprising: an end plate assembly having a motor bracket portion providing a cavity, field laminations axially displaced from and located adjacent said cavity, and a thermal device having a mount end inserted into said cavity, said thermal device being secured to the motor-fan unit through a frictional fit established by the contact between said thermal device and said cavity and said field laminations. Independent claims to be added before filing.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially sectioned front elevational view of a prior art motor-fan unit with the left half of the cover removed to show details of the motor assembly, end plate assembly, diffuser assembly, and fan assembly;

FIG. 2 is a bottom plan view of a prior art thermal device mounting to a motor-fan unit as in FIG. 1;

FIG. 3 is a side elevation view of the mounting of a thermal device to a motor-fan unit in accordance with this invention;

FIG. 4 is an exploded view of a portion of the motor bracket portion of the motor-fan unit of this invention, shown contoured to receive a thermal device in accordance with this invention; and

FIG. 5 is a bottom plan view of the mounting of a thermal device to a motor-fan unit as in FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to FIGS. 3-5, it can be seen that a motor-fan unit in accordance with this invention is designated by the numeral 110. The motor-fan unit 110 is substantially identical to the motor-fan unit 10 of the prior art as shown in FIG. 1. Thus, many elements of the motor-fan unit 110 need not be repeated here. Rather, the focus here is on the mounting of a thermal device 200 to the motor-fan unit 110.

As can be seen, the thermal device 200 is received, at a mount end 202 thereof, in motor bracket portion 137 of end plate assembly 135. More particularly, the motor bracket portion 137 is bowed outwardly as at 138 to provide a cavity 150 that can receive the mount end 202 of the thermal device 200. The remainder of the thermal device 200 extends out of the cavity 150 along side the field laminations 152. Preferably a frictional fit is established between mount end 202 and bowed portion 138 and field laminations 152. A sensor 204 is mounted at the field laminations 152, and is enclosed in a Mylar pocket 206. As seen in FIG. 6, the thermal device 200 and field laminations 152 can both be enclosed in a foam sleeve 208, which may be held by cable tie 210.

The thermal device 200, particularly the sensor 204, measures the general ambient temperature at the locality where it is place, and does not inappropriately measure the amperage or temperature at the field coil. As a result, it is a more reliable thermal device, because it will not incorrectly process that the motor-fan unit is operating at an acceptable temperature, as it might if it were mounted to the field coil. The thermal device 200 and the adaptation made to motor bracket portion 137 also permit the thermal device 200 to be more easily mounted to a motor-fan unit, negating the need for taping and/or cable ties. This will decrease the cost of manufacture.

In light of the foregoing, it should thus be evident that the process of the present invention, providing a motor-fan unit with a thermal device, substantially improves the art. While, in accordance with the patent statutes, only the preferred embodiments of the present invention have been described in detail herein above, the present invention is not to be limited thereto or thereby. Rather, the scope of the invention shall include all modifications and variations that fall within the scope of the attached claims. 

1. A motor-fan unit comprising: an end plate assembly having a motor bracket portion providing a cavity; field laminations axially displaced from and located adjacent said cavity; and a thermal device having a mount end inserted into said cavity, said thermal device being secured to the motor-fan unit through a frictional fit established by the contact between said thermal device and said cavity and said field laminations. 